BR112021003131A2 - methods and systems for treating water containing phosphogypsum - Google Patents

Abstract

METHODS AND SYSTEMS FOR TREATMENT OF WATER CONTAINING PHOSPHAGES. These are methods of treating water containing phosphogypsum. Water can be treated for the purpose of promoting precipitation of one or more target constituents and facilitating downstream membrane treatment. A coagulant can be added to promote phosphate recovery. Ammonia can optionally be removed. Related systems are also revealed.

Description

"METHODS AND SYSTEMS TO TREAT WATER CONTAINING PHOSPHAGES" CROSS REFERENCE TO RELATED ORDERS

[001] This application claims priority for the Provisional Patent Application under Serial No. US 62/720,566 filed on August 21, 2018 and entitled "METHOD AND SYSTEM TO TREAT PHOSPHOGYPSUM CONTAINING WASTEWATER", for the Provisional Patent Application under Serial No. US 62/770,470 filed on November 21, 2018 and entitled "IMPROVED

LIMING PROCESS OF ACIDIC WATER FOR PHOSPHATE RECOVERY AND SCALING REDUCTION FOR DOWNSTREAM PROCESSES", for Provisional Patent Application under Serial No. US 62/798,696 filed on January 30, 2019 and entitled "AMMONIA/AMMONIUM REDUCTION DURING INDUSTRIAL ACIDIC WASTEWATER TREATMENT ” and to the Provisional Patent Application under Serial No. US 62/846,952 filed on May 13, 2019 and entitled “USING MONO-VALENT CATION SELECTIVE AND ANION EXCHANGE MEMBRANES IN ELECTRODIALYSIS TO TREAT DOUBLE LIME TREATED POND WATER”, whose full disclosure of each of which is incorporated in its entirety by the same by reference herein for all purposes.

FIELD OF TECHNOLOGY

[002] Aspects refer, in general, to the treatment of water and, more specifically, to the treatment of water containing phosphogypsum.

BACKGROUND

[003] Phosphoric acid is a precursor compound in the manufacture of many common fertilizers. Phosphogypsum is a by-product of producing phosphoric acid when treating phosphate ore with sulfuric acid. The reaction produces an aqueous slurry of phosphogypsum, phosphoric acid and a liquid by-product stream. The by-product stream is typically reused for cooling, but ultimately stored in large open compartments called phosphogypsum stacks or reservoirs.

[004] This wastewater associated with and produced by phosphate manufacturing operations is typically acidic and typically contains several dissolved constituents such as fluoride, ammonia, silica, sulfate, calcium, heavy metals, phosphate, magnesium, colloidal matter, organic carbon and, in some cases radium (a radioactive element). Reservoirs associated with phosphate processing contain billions of gallons of this wastewater, eg 3 billion gallons each. Due to increasingly strict environmental regulations and annual rainfall, piles need to be treated and closed by operating companies. Reservoir water has become one of the biggest responsibilities of phosphoric acid producers. There is an urgent environmental need to treat this wastewater, particularly in environmentally sensitive areas, or areas where population growth is in closer contact with phosphate processing sites. Treating this wastewater to reduce its toxicity and volume was a technological challenge of significant interest. Toxic and harmful contaminants must be reduced or eliminated before treated water can be discharged into the environment.

[005] A conventional approach that can be used to dispose of wastewater with phosphogypsum is injection into deep wells. This process injects wastewater underground between impermeable layers of rock to prevent pollution of freshwater supplies. Appropriate geology is required for deep well injection sites, and a permit must be obtained before injecting process water underground. Additionally, phosphate is not recoverable from process water in a deep well injection process.

SUMMARY

[006] According to one or more aspects, a method of treating water containing phosphogypsum is disclosed. The method may comprise precipitating at least one target constituent of the phosphogypsum-containing water to produce a supernatant water, introducing a free metal or a salt thereof into the supernatant water to provide a pretreated supernatant water, subjecting the pretreated supernatant water. treated to membrane separation to produce treated water having at least a predetermined discharge requirement and a concentrate stream, removing ammonia from at least one of the pretreated supernatant water and the concentrate stream, and discharging the treated water.

[007] In some respects, precipitation is promoted in a multi-stage process. Calcium and/or magnesium can be precipitated in a first precipitation step. Phosphate can be precipitated in a second precipitation step. The method may further comprise adjusting a pH level of the phosphogypsum-containing water to a first pH level in the first precipitation step. The method may further comprise adjusting the first pH level to a second pH level in the second precipitation step. In some aspects, the method may further comprise a third precipitation step.

[008] In some aspects, the method may further comprise recovering calcium fluoride from an aqueous precipitation slurry associated with the first precipitation step. Similarly, the method may further comprise recovering phosphate from an aqueous precipitation slurry associated with the second precipitation step.

[009] In some aspects, the free metal or salt thereof can be introduced into the supernatant water through chemical or electrolytic addition. The free metal or salt thereof can be an aluminum salt or an iron salt. The method may further comprise recovering phosphate from the pretreated supernatant after introducing the free metal or salt thereof.

[010] In some aspects, membrane separation may involve one or more of nanofiltration, ultrafiltration and reverse osmosis. Membrane separation can involve reverse osmosis and one of nanofiltration and ultrafiltration.

[011] In some respects, the predetermined discharge requirement refers to a level of phosphorus or silica. The method may further comprise recycling at least one reject stream back to a water source containing phosphogypsum.

[012] In some respects, ammonia can be removed from the concentrate stream. Ammonia can be removed from pretreated supernatant water. An ammonia concentration in a water source containing phosphogypsum can be maintained or reduced. In at least some respects, at least 90% ammonia is recovered. The method may further comprise delivering the recovered ammonia as a fertilizer product.

[013] According to one or more embodiments, a system for treating water containing phosphogypsum is disclosed. The system may comprise a water source containing phosphogypsum, a pretreatment subsystem comprising at least one fluidly connected precipitation unit downstream of the water source containing phosphogypsum, a source of a coagulant comprising a free metal or salt thereof fluidly connected to the pretreatment subsystem, a membrane separation subsystem fluidly connected downstream of the pretreatment subsystem and configured to produce treated water that has at least a predetermined discharge requirement, an ammonia removal subsystem in fluid communication with the membrane separation subsystem, and a pretreated water outlet.

[014] In some aspects, the pre-treatment subsystem can comprise at least two precipitation units. The coagulant source may comprise an electrocoagulation subsystem.

[015] In some aspects, the membrane separation subsystem may comprise one or more of a nanofilter, an ultrafilter and a reverse osmosis unit. The membrane separation subsystem may comprise a reverse osmosis unit and one of a nanofilter and an ultrafilter.

[016] In some aspects, the pre-treatment subsystem may additionally comprise at least one clarifier. The pretreatment subsystem may additionally comprise at least one filter press. The pretreatment subsystem may further comprise a sedimentation reservoir.

[017] In some aspects, the system can further comprise a sensor configured to detect at least one operational parameter associated with the water source, the pre-treatment subsystem, the membrane separation subsystem or the treated water outlet. The sensor can be a flow rate, pH, temperature, conductivity, hardness or concentration sensor.

[018] In some aspects, the system may further comprise a controller in communication with the at least one sensor and configured to adjust at least one operating parameter of the system. The controller can be configured to adjust a flow rate or pH level in response to sensor input. The controller can be configured to adjust the fractionation between at least one precipitation unit in order to optimize phosphate recovery. The controller can be configured to adjust an amount of coagulant introduced in order to optimize phosphate recovery.

[019] In some aspects, the ammonia removal subsystem can be configured to remove ammonia from a concentrate stream associated with the membrane separation subsystem. The ammonia removal subsystem can be configured to remove ammonia upstream of the membrane separation subsystem. The ammonia removal subsystem can be configured to maintain or reduce an ammonia concentration in the phosphogypsum-containing water source. In certain respects, the ammonia removal subsystem can be configured to recover ammonia at a rate of at least 90%. The ammonia removal subsystem may comprise a gas transfer membrane contactor.

[020] The disclosure contemplates all combinations of any one or more of the foregoing aspects and/or embodiments, as well as combinations with any one or more of the embodiments set forth in the detailed description and in any examples.

BRIEF DESCRIPTION OF THE DRAWINGS

[021] The attached drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in several figures is represented by a like number. For the sake of clarity, not every component can be identified in each drawing. In the drawings:

[022] Figures 1 to 2 show process flowcharts according to one or more disclosed modalities;

[023] Figure 3 presents a flowchart of processes including an additional solids removal step according to one or more disclosed modalities; and

[024] Figure 4 presents a flowchart of processes including ammonia removal operations according to one or more revealed modalities.

DETAILED DESCRIPTION

[025] According to one or more modalities, water containing phosphogypsum can be efficiently brought within pre-established environmental discharge limits. As used herein, the term water containing phosphogypsum may be interchangeably referred to herein as wastewater or process water. Relevant discharge limits may be established by various local, state, federal or private agencies. For example, the State of Florida has set a maximum conductivity limit of 1.275 µs/cm for the National Pollutant Discharge Elimination System (NPDES) permit. Conventionally, phosphogypsum wastewater can be treated and diluted up to five to ten times to meet conductivity, concentration, and/or charge-based limits for ammonia, fluoride, phosphorus, or other constituents. Water consumed for dilution is typically fresh or treated water that could be used for other purposes. The dilution water can be relatively expensive treated water, such as reverse osmosis product water.

In at least some modalities, a cost-competitive alternative to conventional treatment methods is presented. In some modalities, the consumption of fresh water associated with environmental discharge can be desirably reduced. In at least some modalities, there is no dilution before discharge.

[026] According to one or more embodiments, various product streams (i.e., phosphoric acid, calcium carbonate and/or ammonium sulfate) can be beneficially recovered in conjunction with the wastewater treatment. In some modalities, overall recovery rates can be increased significantly. In certain modalities, a recovery rate of at least about 30%, 40%, 50% or more can be achieved.

[027] According to one or more modalities, wastewater with phosphogypsum can originate from a phosphate manufacturing operation and be stored in a reservoir or pile. Phosphogypsum wastewater can be highly acidic, that is, have a pH level of about 1.5 to about 2 and be environmentally harmful. A non-limiting example of the typical chemical composition of reservoir water is shown in Table 1. In addition to what is shown, the ammonia concentration can be in the range of a few hundred ppm to a few thousand ppm.

TABLE 1 Parameter* pH Range, Standard Units 1.6 to 2.1 Total Acidity, as CaCO3 20,000 to 60,000 Fluoride, as F 4,000 to 12,000 Phosphorus, as P 4,000 to 9,000 Silicon, as Si 1,000 to 3,000 Total Solids 20,000 to 50,000 Total Suspended Solids 50 to 250 Conductivity, µs/cm 15,000 to 40,000 Chlorides, as Cl 50 to 500 Sulphates, as SO4 2,000 to 12,000 Sodium, as Na 50 to 3,000 Calcium, as Ca 50 to 1,500 Magnesium, Mg 50 to 400 Aluminum, as Mg 50 to 1000 Chromium as Cr 0.2 to 5.0 Zinc as Zn 1.0 to 5.0 Iron as Fe 100 to 250 Manganese as Mn 5 to 30 NH3-N as N 0 to 1200 Total Organic N, such as N 3 to 30 Color, APHA units 20 to 4,000 *All values expressed as mg/l unless otherwise noted

[028] According to one or more modalities, the wastewater containing phosphogypsum can be pretreated. Pre-treatment can promote the removal of at least one target species and/or adjust one or more operational parameters in order to facilitate downstream operations. A pretreated supernatant can be delivered to downstream unit operations for further treatment.

[029] According to one or more modalities, pretreatment may involve precipitation. Precipitation can be strategically programmed in stages in order to promote the removal of several target constituents in series. Different target constituents can precipitate under different conditions. For example, a first target constituent might precipitate under a first pH condition and a second target constituent might precipitate under a second pH condition.

[030] According to one or more modalities, the pretreatment may involve adjusting a hardness level. In some non-limiting modalities, magnesium and/or calcium levels may be sought. The hardness level can be adjusted by precipitation in a first pre-treatment stage.

[031] According to one or more modalities, pretreatment may involve phosphate removal. Phosphate removal can be promoted through precipitation in a second pre-treatment stage.

[032] According to one or more modalities, pretreatment may involve adjusting a process stream to a first pH level in a first pretreatment stage to promote precipitation of a first target constituent. Pretreatment may subsequently involve adjusting a process stream to a second pH level of the first pH level in a second pretreatment stage to promote precipitation of a second target constituent.

[033] According to one or more modalities, the pretreatment may further involve promoting the recovery of one or more constituents, such as phosphorus or silica. In some embodiments, a coagulant can be introduced. In certain embodiments, a free metal or salt thereof can be strategically dosed as a coagulant. In some embodiments, an aluminum salt (ie, aluminum sulfate) or an iron salt can be dosed as a coagulant. In at least some non-limiting embodiments, a multivalent metal coagulant can be strategically dosed.

[034] According to one or more modalities, the coagulant can be introduced through chemical or electrolytic addition. Since process water can contain saturated amounts of silica, among other species, the addition of free metals can coagulate and reduce silica levels to acceptable levels for downstream membrane processes. Chemical addition can involve addition of aluminum sulfate, sodium aluminate, iron chloride or other catalyst. Electrolytic addition may involve electrolysis of anodes consisting of aluminum, other aluminum composites, iron/steel or other material. As an example, any commercially available aluminum or iron salts (eg Al2(SO4)3, AlCl3, NaAlO2, Al(NO3)3 can possibly be used as a coagulant to reduce the silica content. than acids in aqueous solution and those which are basic to further reduce or eliminate pH adjustment, eg Al(SO4)3 + NaAlO2.

[035] According to one or more modalities, pre-treatment can significantly increase the recovery efficiency of upstream unit operations. In some embodiments, pretreatment may be performed upstream of a membrane separation subsystem as described herein.

[036] A process flowchart according to one or more non-limiting modalities is shown in Figure 1. A first compound (ie limestone) can be introduced to reach a first target pH level in order to promote a first precipitation . Clarification and filter press or any other related techniques known to those skilled in the art can be used to recover a first precipitate (ie, calcium fluoride). The first precipitation can generally reduce a hardness level of a process stream that enters a second precipitation. A second compound (ie, residual lime) can be introduced to reach a second target pH level to promote the second precipitation. The second pH level can generally be different from the first pH level. In at least some embodiments, the second pH level can be higher than the first pH level. The second precipitation can generally promote precipitation of an aqueous phosphate slurry that can be delivered for further processing and recovery. A coagulant can then be added to further promote phosphate recovery. A process stream dosed with coagulant can be introduced into a sedimentation reservoir for a predetermined period of time, ie several hours. A pH level of a process stream in the settling vessel can optionally be readjusted. The sedimentation operation can generally promote precipitation of an additional aqueous phosphate slurry that can be delivered for further processing and recovery. A pretreated supernatant can then be delivered downstream for further processing, i.e. via membrane separation. For example, non-limiting membrane separation operations can include one or more of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). Figure 1 presents a modality in which NF and RO are implemented in series. Figure 2 presents an alternative modality in which NF and RO in stages are implemented in series.

[037] According to one or more modalities, an additional solid waste recovery step can be incorporated as shown in Figure 3.

The additional solid waste recovery step can be presented with an intermediate pH level between the first and second pH levels.

[038] According to one or more modalities, several stages of pretreatment can be strategically controlled in order to promote the recovery of several target compounds. The downstream recovery process can also be optimized. In some embodiments, an amount of coagulant, i.e. aluminum, added can be strategically controlled in order to optimize recovery and downstream processes. In some embodiments, fractionation (ie, pH breakpoints) associated with pretreatment precipitation can be strategically controlled to optimize recovery and downstream processes. Waiting periods, ie inside clarifiers, and sedimentation reservoir time can also be optimized or reduced.

[039] Ammonia/ammonium can become increasingly concentrated or enriched over time as various reject streams from membrane processes are recycled back into the reservoir. According to one or more modalities, systems and methods can beneficially remove ammonia.

[040] According to one or more modalities, ammonia desorption and/or recovery processes can be strategically integrated. For example, ammonia can be removed downstream of any silica or phosphate reduction process. Additionally or alternatively, ammonia can also be removed from rejection currents associated with various membrane processes. A flow rate of an ammonia desorption/recovery process can be strategically adjusted so that a reservoir ammonia concentration or content can be maintained or reduced rather than increased. In some non-limiting embodiments, ammonia removal can be accomplished through membrane degassing, i.e., with a gas transfer membrane contactor. For example, a commercially available Liqui-Cel™ gas transfer membrane contactor from 3M Company can be implemented. In some embodiments, the gas transfer membrane contactor can remove about 90% to about 99% of ammonia from a process stream. In at least some modalities, ammonium sulfate can be recovered.

[041] Figure 4 presents a flowchart of processes according to one or more modalities that implement an ammonia desorption/recovery process. Alternative positions for ammonia removal are indicated. The ammonia/ammonium concentration can beneficially be kept relatively stable or reduced. This can make it possible to handle a simpler pile closure task at a later stage, as well as recovering the ammonia/ammonium value as ammonium sulfate fertilizer.

[042] According to one or more embodiments, a treatment system may include at least one sensor configured to detect an operational parameter. For example, the sensor can be configured to detect an operating parameter associated with the reservoir water source, the pre-treatment system, i.e., a precipitation subsystem, the membrane subsystem, the ammonia removal subsystem or the outlet of treated water. In some non-limiting embodiments, the sensor may be a flow rate, pH, temperature, conductivity, hardness, or concentration sensor. In some embodiments, two or more sensors, for example a plurality of sensors, can be incorporated. Sensors can be strategically placed throughout the system. Sensors can be interrelated and/or interconnected, for example in relation to process control. The system may additionally include a controller in communication with the at least one sensor. The controller can be configured to provide a control signal in response to sensor input. For example, the controller can provide a control signal to actuate or adjust a valve in the system or subsystem thereof. In some non-limiting modes, the controller can be configured to adjust a flow rate or pH level in response to sensor input. The controller can adjust the addition of coagulant in response to sensor input. In this way, the controller can enable the adjustment of one or more process parameters in order to produce one or more streams of desirable products. In some non-limiting embodiments, the controller can adjust the flux to a membrane contactor, for example, to promote ammonium sulfate recovery as described herein. The controller can be additionally configured to make a comparison between a measured value and a predetermined value, such as an established discharge requirement, and adjust various control settings accordingly.

[043] The function and advantages of these and other modalities can be better understood from the following examples. The examples are intended to be illustrative in nature and not to be considered as limiting the scope of the invention.

EXAMPLE 1

[044] A process flowchart according to Figure 1 was tested in the laboratory and modeled. A projected water analysis from modeling is shown in Table 2A.

[045] Sample reservoir water containing phosphogypsum that has a pH of about 2.7 was reacted with limestone at a target pH level of 4 to 4.5 on a rating scale. After sedimenting for approximately 20 minutes, the aqueous slurry was filtered to recover water to be combined with a supernatant decanted effluent stream (for increased overall water recovery). Solids are designed to have amounts of calcium fluoride, calcium phosphate, silica precipitates, to be further treated as solid waste.

Additionally, treatment of the combined supernatant from pH 4 to 4.5 to a target pH level of 7 to 7.5 was carried out using residual lime (Ca(OH)2) at the laboratory scale. This second precipitation step generated a sizable portion of calcium phosphate precipitates. This water slurry from the second clarifier must be pumped to an upstream acid plant for phosphate recovery. The value of phosphate recovered for an active installation is considerable and must be observed. The supernatant that has been decanted from the second precipitation step after sedimenting for approximately 20 minutes follows a third precipitation step. To reduce silica and phosphate in the second supernatant solution, aluminum was added as aluminum sulfate. Laboratory results of alum additions are shown in Table 2B for reduction in SiO2 levels. Silica reduction facilitates superior upstream water recovery operations. This treated supernatant was then introduced into a sedimentation reservoir to sediment aqueous aluminum phosphate slurry, which can be further treated for phosphate recovery, or considered as solid waste. The effluent from the sedimentation reservoir can be filtered in NF/RO downstream.

TABLE 2A Parameter Feeding Unit Supernatant Supernatant Supernatant from (10/04/2018) Precipitation n° 1 Precipitation n° 2 Precipitation n° 3 Volume of ml 50 43 34 35 sample Dry g mass - 3.353 1.07 0.2 precipitated Calcium mg/l 3310 4625 320 146 as CaCO3 Magnesium mg/l 1510 916 43 34 as CaCO3 Sodium mg/l 5490 6150 6150 6150 as CaCO3 Potassium mg/l 370 500 500 500 as CaCO3 Iron mg/l 169 0.0 0 ,0 0.0 Manganese mg/l 25 2.2 2.2 2.2 Aluminum mg/l 161 0.1 0.1 0.1 Barium mg/l 0 1.9 1.9 1.9 Strontium mg/ l 48 48 48 48 Copper mg/l 0 - - - Zinc mg/l 18 - - - Bicarbonate mg/l - - - as CaCO3 Fluoride mg/l 19500 81 52 0 as CaCO3 Chloride mg/l 262 262 262 262 as CaCO3 Bromide mg/l 0 - - - as CaCO3 Nitrate mg/l 46 12.3 12.3 12.3 as CaCO3 Phosphate mg/l 51500 22430 4966 2092 as CaCO3 Sulphate mg/l 7840 5097 4815 4911 as

CaCO3 pH 2.7 4.5 7.4 7.1 Turbidity NTU 28 - - - Conductivity µs/cm 36900 - - - Total Hardness mg/l 4681 - - - as CaCO3 TOC mg/l 192 53 53 53 Mineral Acidity mg /l 26864 - - - as CaCO3 Ammonia mg/l 4531 4531 4531 <4531 as CaCO3 Total Silica mg/l 3045 451 183 101 as CaCO3 Total Acidity mg/l 47633 - - as CaCO3

TABLE 2B Ratio of Al:SiO2 (mass) pH Time Al SiO2 SiO2 (mg/l) Elapsed (h) 3.5 4.5 1 2 614 3.5 20 1 2 379 3.5 20 1 2 346 4.5 4,5 1 2 445 4,5 20 1 2 285 4,5 20 1 2 281 5,5 4,5 1 2 330 5,5 20 1 2 253 5,5 20 1 2 288 5,5 16 5 1 609 5.5 16 5 1 560 7.3 16 6 1 80 7.3 16 6 1 86 7.3 17 2 1 17 7.3 17 2 1 17 7.6 17 1 2 19 7.6 17 1 2 18 8 ,9 17 1 8 83 8.9 17 1 8 86 7.3 4 N/AN/A 186 7.3 4 N/AN/A 184 7.3 94 N/AN/A 155 7.3 94 N/AN /A 151 7.3 18 1 8 131 7.3 18 1 8 131 6.7 18 1 8 177

6.7 18 1 8 175 7.3 18 1 2 27 7.3 18 1 2 27 7.3 18 1 4 78 EXAMPLE 2

[046] A process flowchart according to Figure 2 was tested in the laboratory and modeled for expansion. A summary of scaled-up current compositions can be seen in Table 3A. Sample reservoir water containing phosphogypsum (500 ml) which has a pH of about 2.0 was reacted with limestone (20.5 g) at room temperature at a target pH level of 3.8. After sedimenting for approximately 30 minutes, the aqueous slurry was filtered to recover water to be combined with a supernatant decanted effluent stream (for increased overall water recovery, 90% net volume relative to feed). Solids were analyzed for the presence of amounts of fluoride, phosphate, silica and magnesium, >98%, >40%, 80% and >25% wt%, respectively, to be further treated as solid waste.

Additionally, treatment of the combined supernatant from pH 3.8 to a target pH level of 7.4 was carried out using residual lime (Ca(OH)2, 4g) at the laboratory scale. This second precipitation step generated a sizable portion of calcium phosphate precipitates (>45% wt% phosphate relative to feed). This water slurry from the second clarifier must be pumped to an upstream acid plant for phosphate recovery. The value of recovered phosphate for an active facility is considerable and would contribute to overall savings. The supernatant that has been decanted (>75% net volume relative to feed) from the second precipitation step after sedimenting for approximately 30 minutes follows a third precipitation step. To reduce silica and phosphate in the second supernatant solution, electrocoagulation (EC) was used. (EC) was evaluated to reduce silica content in water containing phosphogypsum without increasing TDS loading. An electrocoagulation reactor was used with a flow of 15 ml/min of sample water with a residence time of 30 minutes in variable current. The data in Table 3B clearly showed that EC can reduce silica in a much shorter time frame and more effectively compared to traditional chemical coagulation. Table 3C presents treated data and Table 3D presents control data.

[047] Furthermore, the results additionally showed that EC (using aluminum electrodes) does not introduce excess aluminum ions into the treated water, which is highly desirable for downstream membrane processes to operate at high recoveries. This supernatant was sedimented for 30 minutes and decanted. Precipitates from the EC step can be further treated for phosphate recovery or considered as solid waste. The sedimentation effluent was analyzed through an in-house laboratory and industrial design software was used to model the downstream membrane processes. The downstream membrane processes were modeled as an UF followed by a 2-pass RO system. The water recoveries for UF and RO with 2 passes are 90%, 60% and 80%, respectively. The 1st RO pass uses SH30H-380 membranes and contains 1 stage with 112 pressure vessels (to achieve scaled-up flow rates). The 2nd RO pass uses BW30-400 membranes and contains 2 stages with 48 pressure vessels in each stage. Operating conditions for both passes are 25 °C ambient with the first pass being low pH RO and near neutral pH RO for the second pass. Antifouling may be required and thus has been modeled in the process. The anti-scalant Chemtreat was used at a dose of 8.7 mg/l in the 1st passage of OR. There may be pH adjustment before going into the 1st RO pass, so sulfuric acid can be used to lower the pH. The 2nd RO permeate pass is designed to meet NPDES discharge limits, and in some cases only a single pass RO is required.

TABLE 3A Parameter Feed Unit Supernatant Supernatant Supernatant UF Permeate unit permeate RO1 rejection RO1 RO2 RO2 de RO1 de silica paste Aqueous gel Reservoir Precipitation Precipitation Precipitation precipitation (17/9/2018) n° 1 n° 2 n° 3 2 Flow GPM 6959 6207 5559 4460 5000 3375 2160 1800 540 648 1099 Volumetric Calcium mg/l 3050 4625 320 3.57 3.57 mg/l 0.02 0.00 71.13 0.10 41552 1604 as CaCO3 Magnesium ion mg/l 1110 916 43 13.9 13.9 mg/l 0.00 0.00 8.45 0.00 8411 159 as as CaCO3 Sodium ion mg/l 5620 6150 6150 5010 5010 mg/l 3.59 0, 04 5791.01 17.80 6150 10777 as as CaCO3 ion

20/28 Potassium mg/l 450 500 500 290 290 mg/l 1.99 0.08 564.07 9.62 500 1352 as as CaCO3 Iron ion mg/l 80 0 0 0.02 0.02 mg/l 0 .00 0.00 0 0.00 0 0 as ion Manganese ion mg/l 14 2 2 0.01 0.01 NA 0.00 NA 0.00 2 11 as Aluminum ion mg/l 108 0 0 0.08 0.08 NA 0.00 NA 0.00 2 as strontium ion mg/l 39 2 2 0.03 0.03 0.00 0.00 0.07 0.00 2 9 as HCO3 ion mg/l <0.0 5 574.4 574.4 mg/l 5.52 1.31 1718.62 26.26 0 -2331 as as CaCO3 Bromide ion mg/l <3 6.05 6.05 NA NA NA NA 0 -25 as CaCO3 Fluoride mg/l 19000 81 52 11 mg/l 0.00 0.00 0.95 0.00 327 258 as as CaCO3 Chloride ion mg/l 147 262 262 190 190 mg/l 0.85 0.02 336, 27 4.17 262 554 as as CaCO3 Nitrate ion mg/l 25 12 12 15.4 15.4 mg/l 1.15 0.28 45.77 4.64 12 0 as as CaCO3 Phosphate ion mg/l 34100 22430 4966 1190 1190 mg/l 1.08 0.04 2103.34 8.02 172233 20290 as as CaCO3 Sulfate ion mg/l 7150 5097 4815 5910 5910 mg/l 11.56 0.74 15869.9 131.10 7512 373 as as CaCO3 ion pH su 2.0 3.8 7.4 8.54 8.54 s.u. 5.21 4.63 7.15 5.84 TDS mg/l 49863 mg/l 28.17 2.81 30773 255.68 as as ion ion Ammonia mg/l mg/l 9.64 2.81 3001.78 46.83 4089.00 as as CaCO3 Total Silica ion mg/1 mg/l 0.60 0.01 146.62 2.96 2750.30 723.63 as as CaCO3 ion

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TABLE 3B Current Test Input Setting Time Output Reduction of No. (A) permanence Silica-Silica Electrode (ppm) (min) (ppm) (ppm) 1 0.5 31 Al(+)/Al/Al/ Al(-) 113 67 46 2 1,0 31 Al(+)/Al/Al/Al(-) 156 62 94 3 1,0 31 Fe(+)/Fe/Fe/Fe(- 156 120 36 ) 4 0.5 31 Fe(+)/Fe/Fe/Fe(- 156 123 33 ) 5 1.0 31 Al(+)/Fe/Al/Fe(-) 147 28 119 14 1.0 31 Al(+) /Al/Al(-) 142 69 73 TABLE 3C

TEST RESULTS UNITS Aluminum (Al) 0.077 mg/l Bicarbonate (HCO3) 574.4 mg/l CaCO3 Bromide (Br) 6.05 mg/l CaCO3 Carbonate (CO3) 232.9 mg/l CaCO3 Chloride (Cl ) 190 mg/l of CaCO3 Fluoride (Fl) <1.00 mg/l of CaCO3 Hydroxide (OH) 0.0 mg/l of CaCO3 Nitrate (NO3) 15.4 mg/l of CaCO3 Phosphate (PO4) 1190 mg /l of CaCO3 Sulfate (SO4) 5910 mg/l of CaCO3 Barium (Ba) <0050 mg/l Calcium (Ca) 3.57 mg/l of CaCO3 Iron (Fe) <0020 mg/l Magnesium (Mg) 13. 9 mg/l of CaCO3 Manganese (Mn) <0020 mg/l Potassium (K) 290 mg/l of CaCO3 Sodium (Na) <0010 mg/l of Free CaCO3 (CO2) 5.3 mg/l of CaCO3 Copper ( Cu) <0020 mg/l Ammonia (NH3) 2246 mg/l CaCO3 pH 8.54 Total Silica 49.29 mg/l CaCO3 Silicon 28 mg/l Strontium 0.031 mg/l Zinc 0.023 mg/l 3D TABLE

TEST RESULTS UNITS Aluminum (Al) 0.087 mg/l Bicarbonate (HCO3) 1352.2 mg/l CaCO3 Bromide (Br) 6.17 mg/l CaCO3 Carbonate (CO3) 0.0 mg/l CaCO3 Chloride (Cl ) 200 mg/l of CaCO3

Fluoride (Fl) <1.00 mg/l of CaCO3 Hydroxide (OH) 0.0 mg/l of CaCO3 Nitrate (NO3) 21.6 mg/l of CaCO3 Phosphate (PO4) 4470 mg/l of CaCO3 Sulphate (SO4 ) 5890 mg/l of CaCO3 Barium (Ba) <0050 mg/l Calcium (Ca) 6.27 mg/l of CaCO3 Iron (Fe) <0020 mg/l Magnesium (Mg) 11.5 mg/l of CaCO3 Manganese (Mn) <0010 mg/l Potassium (K) 310 mg/l of CaCO3 Sodium (Na) 5310 mg/l of Free CaCO3 (CO2) 53.4 mg/l of CaCO3 Copper (Cu) <0020 mg/l Ammonia (NH3) 3325 mg/l of CaCO3 pH 7.76 Total Silica 119.13 mg/l of CaCO3 Silicon 67 mg/l Strontium 0.032 mg/l Zinc <0020 mg/l

[048] Table 4 shows the results in silica concentration with a 1:1 ratio of silica to alum as a coagulant.

TABLE 4

TEST RESULTS UNITS Aluminum (Al) 0.281 mg/l Bicarbonate (HCO3) 474.4 mg/l of CaCO3 Bromide (Br) 6.04 mg/l of CaCO3 Carbonate (CO3) 0.0 mg/l of CaCO3 Chloride (Cl ) 169 mg/l of CaCO3 Fluoride (Fl) <1.00 mg/l of CaCO3 Hydroxide (OH) 0.0 mg/l of CaCO3 Nitrate (NO3) 18.2 mg/l of CaCO3 Phosphate (PO4) 1770 mg /l of CaCO3 Sulfate (SO4) 6590 mg/l of CaCO3 Barium (Ba) <0050 mg/l Calcium (Ca) 4.24 mg/l of CaCO3 Iron (Fe) <0020 mg/l Magnesium (Mg) 0.858 mg /l of CaCO3 Manganese (Mn) <0010 mg/l Potassium (K) 260 mg/l of CaCO3 Sodium (Na) 5080 mg/l of Free CaCO3 (CO2) 62.1 mg/l of CaCO3 Copper (Cu) < 0020 mg/l Ammonia (NH3) 3005 mg/l CaCO3 pH 7.24

Total Silica 45.48 mg/l CaCO3 Silicon 26 mg/l Strontium <0010 mg/l Zinc <0020 mg/l

[049] Table 5 shows the control without added coagulant.

TABLE 5

TEST RESULTS UNITS Aluminum (Al) 0.087 mg/l Bicarbonate (HCO3) 1352.2 mg/l CaCO3 Bromide (Br) 6.17 mg/l CaCO3 Carbonate (CO3) 0.0 mg/l CaCO3 Chloride (Cl ) 200 mg/l of CaCO3 Fluoride (Fl) <1.00 mg/l of CaCO3 Hydroxide (OH) 0.0 mg/l of CaCO3 Nitrate (NO3) 21.6 mg/l of CaCO3 Phosphate (PO4) 4470 mg /l of CaCO3 Sulfate (SO4) 5890 mg/l of CaCO3 Barium (Ba) <0050 mg/l Calcium (Ca) 6.27 mg/l of CaCO3 Iron (Fe) <0020 mg/l Magnesium (Mg) 11, 5 mg/l of CaCO3 Manganese (Mn) <0010 mg/l Potassium (K) 310 mg/l of CaCO3 Sodium (Na) 5310 mg/l of Free CaCO3 (CO2) 53.4 mg/l of CaCO3 Copper (Cu ) <0020 mg/l Ammonia (NH3) 3325 mg/l CaCO3 pH 7.76 Total Silica 119.13 mg/l CaCO3 Silicon 67 mg/l Strontium 0.032 mg/l Zinc <0020 mg/l

[050] Table 6 shows the results in silica concentration when using an aluminum electrode in an electrocoagulation process.

TABLE 6

TEST RESULTS UNITS Aluminum (Al) 0.077 mg/l Bicarbonate (HCO3) 574.4 mg/l CaCO3 Bromide (Br) 6.05 mg/l CaCO3 Carbonate (CO3) 232.9 mg/l CaCO3 Chloride (Cl ) 190 mg/l of CaCO3

Fluoride (Fl) <1.00 mg/l of CaCO3 Hydroxide (OH) 0.0 mg/l of CaCO3 Nitrate (NO3) 15.4 mg/l of CaCO3 Phosphate (PO4) 1190 mg/l of CaCO3 Sulphate (SO4 ) 5910 mg/l of CaCO3 Barium (Ba) <0050 mg/l Calcium (Ca) 3.57 mg/l of CaCO3 Iron (Fe) <0020 mg/l Magnesium (Mg) 13.9 mg/l of CaCO3 Manganese (Mn) <0010 mg/l Potassium (K) 290 mg/l CaCO3 Sodium (Na) 5010 mg/l Free CaCO3 (CO2) 5.3 mg/l CaCO3 Copper (Cu) <0020 mg/l Ammonia (NH3) 2246 mg/l of CaCO3 pH 8.54 Total Silica 49.29 mg/l of CaCO3 Silicon 28 mg/l Strontium 0.031 mg/l Zinc 0.023 mg/l

[051] Table 7 shows the results in silica concentration when using a 1:1 ratio of silica to ferric salts as a coagulant.

TABLE 7

TEST RESULTS UNITS Aluminum (Al) 0.066 mg/l Bicarbonate (HCO3) 868.9 mg/l CaCO3 Bromide (Br) 6.14 mg/l CaCO3 Carbonate (CO3) 0.0 mg/l CaCO3 Chloride (Cl ) 938 mg/l of CaCO3 Fluoride (Fl) <1.00 mg/l of CaCO3 Hydroxide (OH) 0.0 mg/l of CaCO3 Nitrate (NO3) 24.0 mg/l of CaCO3 Phosphate (PO4) 3180 mg /l of CaCO3 Sulfate (SO4) 5810 mg/l of CaCO3 Barium (Ba) <0050 mg/l Calcium (Ca) 10.4 mg/l of CaCO3 Iron (Fe) <0020 mg/l Magnesium (Mg) 5, 15 mg/l of CaCO3 Manganese (Mn) <0010 mg/l Potassium (K) 290 mg/l of CaCO3 Sodium (Na) 5140 mg/l of Free CaCO3 (CO2) 55.7 mg/l of CaCO3 Copper (Cu) ) < Ammonia (NH3) 3240 mg/l of CaCO3 pH 7.55 Total Silica 114.79 mg/l of CaCO3 Silicon 64 mg/l Strontium <0010 mg/l Zinc <0020 mg/l EXAMPLE 3

[052] Referring to Figure 4, an ammonia recovery process can be integrated according to one or more modalities. Due to the high levels of ammonia in certain wastewaters, a dedicated ammonia treatment process may be required prior to membrane systems as well as to treat concentrate from membrane systems. Ammonia reduction from wastewater can consist of desorption and air bubble formation through concentrated acid, or the use of other technologies, such as other technologies, such as a membrane contactor. In this example, a membrane contactor using sulfuric acid was considered to treat the ammonia with the current that enters after the EC process. Table 8 presents simulated data from a 1000 gpm NH3-N Liqui-Cel™ recovery system at varying recoveries. The ammonia recovery process typically requires higher pH (8.5 to 11 s.u.) to proceed and 90 to 99% ammonia/ammonium can be recovered depending on operating conditions. Ammonium sulfate can be readily reused as a fertilizer and resold.

TABLE 8 NH3-N removal and recovery >90% >95% >99% target in the system Contactor Size/Type 14x28x50 14x28x50 14x28x50 Membrane Ammonia-water flow rate 1000 1000 1000 design serving, gpm Ammonia-water temperature 50 50 50 design, °C Recommended acid user for Acid Acid Acid capture Sulfuric ammonia; Sulfuric; Sulfuric; Recommended adjusted pH of water with 10 10 10 ammonia considered pH of acidic solution that <2 <2 <2 enters contactors Incoming NH3-N concentration

3,000 3,000 3,000 design, ppm Number of contactors in parallel 18 16 24 Number of contactors in series 2 3 3 # of contactors required, total 36 48 72 Designed NH3-N concentration 255 117 31 after system, ppm NH3- removal N designed in 91% 96% 99% system CIRCULATION Rate of acid desorption required (Total System). 637 1021 1096 Ibs/h Ammonia Removal Rate, Ibs/h 1374 1444 1486 Calculated Acid CONSTITUTION Rate Required (System Total), 3961 4161 4284 gpm Calculated Sulfate Production Rate, 5335 5604 5770 Ibs/h Waste Water of estimated system DO, 5 9 6 psi Estimated Acid Solution, psi 11 16 12

[053] The phraseology and terminology used in this document is for the purpose of description and should not be considered limiting. As used herein, the term “plurality” refers to two or more items or components. The terms "comprising", "including", "carrying", "having", "containing" and "involving", whether in the written description or in the claims and the like, are terms of free interpretation, that is, to mean "including, but not limited to”. Therefore, the use of such terms shall cover the items listed below, and equivalents thereof, as well as additional terms. Only the transitional expressions, “consisting of” and “consisting essentially of”, are expressions of restricted or semi-restricted interpretation, respectively, in relation to the claims. The use of ordinal terms such as "first", "second", "third" and the like in claims to modify a claim element does not by itself connote any priority, precedence or order of a claim element over another or the temporal order in the which acts of a method are performed, but are used merely as identifications to distinguish a claiming element having a certain name from another element having the same name (but to use the ordinal term) to distinguish the claiming elements.

[054] Having thus described various aspects of at least one modality, it should be noted that various changes, modifications, and enhancements will readily occur to those skilled in the art. Any feature described in any modality may be added to or replaced with any feature of any other modality. Such changes, modifications and enhancements are intended to be part of this disclosure and are intended to be within the scope of the invention. Therefore, the above description and drawings are by way of example only.

[055] Those skilled in the art should note that the parameters and configurations described in this document are exemplary and that actual parameters and/or configurations will depend on the specific application in which the disclosed methods and materials are used. Those skilled in the art must recognize or be able to verify, using no more than routine experimentation, equivalents to the specific modalities disclosed.

Claims (40)

1. Method of treatment of water containing phosphogypsum CHARACTERIZED by the fact that it comprises: promoting the precipitation of at least one target constituent of the water containing phosphogypsum to produce a supernatant water; introducing a free metal or salt thereof to the supernatant water to provide a pretreated supernatant water; subjecting the pretreated supernatant water to membrane separation to produce treated water having at least a predetermined discharge requirement and a concentrate stream; removing ammonia from at least one of the pretreated supernatant water and concentrate stream; and discharge the treated water. 2. Method according to claim 1, CHARACTERIZED by the fact that precipitation is promoted in a multi-stage process. 3. Method according to claim 2, CHARACTERIZED by the fact that calcium and/or magnesium is precipitated in a first precipitation step. 4. Method according to claim 3, CHARACTERIZED by the fact that phosphate is precipitated in a second precipitation step. 5. Method according to claim 2, characterized in that it further comprises adjusting a pH level of the water containing phosphogypsum to a first pH level in the first precipitation step. 6. Method according to claim 5, characterized in that it further comprises adjusting the first pH level to a second pH level in the second precipitation step. 7. Method according to claim 4, CHARACTERIZED by the fact that it additionally comprises a third precipitation step. 8. Method according to claim 3, characterized in that it further comprises recovering calcium fluoride from an aqueous precipitation slurry associated with the first precipitation step. 9. Method according to claim 4, CHARACTERIZED in that it further comprises recovering phosphate from an aqueous precipitation slurry associated with the second precipitation step. 10. Method according to claim 1, CHARACTERIZED by the fact that the free metal or salt thereof is introduced into the supernatant water through chemical or electrolytic addition. 11. Method according to claim 10, CHARACTERIZED by the fact that the free metal or salt thereof is an aluminum salt or an iron salt. 12. Method according to claim 10, CHARACTERIZED by the fact that it further comprises recovering phosphate from the pretreated supernatant after the introduction of the free metal or salt thereof. 13. Method according to claim 1, CHARACTERIZED by the fact that membrane separation involves one or more of nanofiltration, ultrafiltration and reverse osmosis. 14. Method according to claim 13, CHARACTERIZED by the fact that membrane separation involves reverse osmosis and one of nanofiltration and ultrafiltration. 15. Method according to claim 1, CHARACTERIZED by the fact that the predetermined discharge requirement belongs to a level of phosphorus or silica. 16. The method of claim 1, characterized in that it further comprises recycling at least one reject stream back to a water source containing phosphogypsum. 17. Method according to claim 1, CHARACTERIZED by the fact that ammonia is removed from the concentrate stream. 18. Method according to claim 1, CHARACTERIZED by the fact that ammonia is removed from the pretreated supernatant water. 19. Method according to claim 1, CHARACTERIZED by the fact that an ammonia concentration in a water source containing phosphogypsum is maintained or reduced. 20. Method according to claim 1, CHARACTERIZED by the fact that at least 90% ammonia is recovered. 21. Method according to claim 20, CHARACTERIZED by the fact that it further comprises delivering the recovered ammonia as a fertilizer product. 22. System for treating water containing phosphogypsum CHARACTERIZED by the fact that it comprises: a water source containing phosphogypsum; a pre-treatment subsystem comprising at least one precipitation unit fluidly connected downstream of the phosphogypsum-containing water source; a source of a coagulant comprising a free metal or salt thereof fluidly connected to the pretreatment subsystem; a membrane separation subsystem fluidly connected downstream of the pretreatment subsystem and configured to produce treated water having at least one predetermined discharge requirement; an ammonia removal subsystem in fluid communication with the membrane separation subsystem; and a treated water outlet. 23. System according to claim 22, CHARACTERIZED by the fact that the pre-treatment subsystem comprises at least two precipitation units. 24. System according to claim 22, CHARACTERIZED by the fact that the coagulant source comprises an electrocoagulation subsystem. 25. System according to claim 22, CHARACTERIZED by the fact that the membrane separation subsystem comprises one or more of a nanofilter, an ultrafilter and a reverse osmosis unit. 26. Method according to claim 25, CHARACTERIZED by the fact that the membrane separation subsystem comprises a reverse osmosis unit and one of a nanofilter and an ultrafilter. 27. System according to claim 22, CHARACTERIZED by the fact that the pre-treatment subsystem additionally comprises at least one clarifier. 28. System according to claim 22, CHARACTERIZED by the fact that the pre-treatment subsystem additionally comprises at least one filter press. 29. System according to claim 22, CHARACTERIZED by the fact that the pre-treatment subsystem additionally comprises a sedimentation reservoir. 30. System according to claim 22, CHARACTERIZED by the fact that it additionally comprises a sensor configured to detect at least one operational parameter associated with the water source, the pre-treatment subsystem, the membrane separation subsystem or the output of treated water. 31. System according to claim 30, CHARACTERIZED by the fact that the sensor is a flow rate, pH, temperature, conductivity, hardness or concentration sensor. 32. System according to claim 31, CHARACTERIZED by the fact that it further comprises a controller in communication with the at least one sensor and configured to adjust at least one operating parameter of the system. 33. System according to claim 32, CHARACTERIZED by the fact that the controller is configured to adjust a flow rate or pH level in response to sensor input. 34. System according to claim 32, CHARACTERIZED by the fact that the controller is configured to adjust the fractionation between the at least one precipitation unit operation in order to optimize phosphate recovery. 35. System according to claim 32, CHARACTERIZED by the fact that the controller is configured to adjust an amount of coagulant introduced in order to optimize phosphate recovery. 36. System according to claim 22, CHARACTERIZED by the fact that the ammonia removal subsystem is configured to remove ammonia from a concentrate stream associated with the membrane separation subsystem. 37. System according to claim 22, CHARACTERIZED by the fact that the ammonia removal subsystem is configured to remove ammonia upstream of the membrane separation subsystem. 38. System according to claim 22, CHARACTERIZED by the fact that the ammonia removal subsystem is configured to maintain or reduce an ammonia concentration in the water source containing phosphogypsum. 39. System according to claim 22, CHARACTERIZED by the fact that the ammonia removal subsystem is configured to recover ammonia at a rate of at least 90%. 40. System according to claim 22, CHARACTERIZED by the fact that the ammonia removal subsystem comprises a gas transfer membrane contactor.